1. Field of the Invention
The resent invention relates to an inverted Galilean finder for a photopraphic camera and, more particularly, to an Albada type of inverted Galilean finder improved in structure.
2. Description of Related Art
Modern compact cameras, widely used for nonprofessional purpose, are typically equipped with various automatic features, such as automatic exposure, automatic focusing, automatic film winding, low luminanee flash exposure, etc. Such an automatic compact camera provides various opportunity of taking pictures with ease for amateur photographers. These automatic compact cameras of the middle class are typically equipped with bright frame finders, such as an illuminating window type bright frame finder whose distinctive feature is a framing line which stands out in bold relief against the field of view. However, because the illuminating window type bright frame finder is necessarily equipped with an illuminating optical system which correlates optically with a finder optical system, it makes the compact camera with various automatic features bulky. For this reason, the automatic compact camera is typically equipped with an Albada type inverted Galilean finder.
For the purpose of providing a brief background of an Albada type finder which will enhance an understanding of the present invention, reference is made to FIG. 1.
Reference to FIG. 1 showing a prior art Albada type finder, the finder optical system is comprised of a bi-convex objective lens 2 and a concave eyepiece 1. Disposed between the objective lens 2 and the concave eyepiece 1 is a concave half mirror 3 with a concave surface directed toward the bi-convex objective lens 2. This half mirror 3 is transmittable a half portion of light over the entire area. A framing line 4 of a metal, such as aluminum, is formed on the surface of the objective lens 2 facing the half mirror 3 by vacuum vapor deposition. If the Albada finder is incorporated in a camera with an automatic focusing feature, a target marking (not shown), in which an object to be focused is positioned, is formed on the surface of the objective lens 2 at a center area of the field of view by vacuum vapor deposition.
However, with the Albada finder of this type having an optical element formed as a half mirror over the entire area, the field of view is lightly colored and/or becomes dimmed. Further, the optical image of the framing line is deteriorated in sharpness and blurred. In addition, the metal deposition of framing line and the use of half mirror increases the cost of optical finder.